Behaviour of a silicon-rich coating on Ti-46Al-8Ta (at.%) in hot-corrosion environments

In this work silicon-rich coating was deposited on a Ti-46Al-8Ta (at.%) alloy in a two-step procedure comprising physical and chemical vapour deposition (magnetron sputtering and pack cementation, respectively). Protective properties of the coating were tested through cyclic oxidation in air at 800 °C with samples contaminated with NaCl, Na2SO4 or a mixture of these two salts. The coated samples exhibited better hot corrosion resistance compared with the uncoated reference. This was attributed to the formation of an oxide layer composed of amorphous silica with embedded rutile and α cristobalite crystals, constituting a barrier against oxygen penetration.